1. Field of the Invention
The present invention relates to a lens position correction device for a lens barrel, and more particularly to a lens position correction device for a lens barrel having a movable and fixed lens barrels and a lens holding frame
2. Description of the Related Arts
A lens barrel of this type will be explained with reference to FIG. 13 by using a zoom lens as an example In general, a zoom lens 100 comprises a movable barrel 10, fixed barrel 20 and lens holding frame 30, all of which overlap A zooming cam channel 11 formed at the movable barrel 10 and a rectilinear channel 21 formed at the fixed barrel 20 cross each other and engage with a cam follower pin 40 fixed to the lens holding frame 30.
Accordingly, when the movable barrel 10 is rotated, the cam follower pin 40 moves along the zooming cam channel 11 while the rotation of the cam follower pin 40 is prevented by the rectilinear channel 21, whereby the lens holding frame 30 moves to thereby obtain a desired zooming.
However, there occurs inevitably a processing error of the movable barrel 10, fixed barrel 20, lens holding frame 30 or the like, a processing error of the zooming cam channel 11 and rectilinear channel 21 and a cumulative error in assembling these members Therefore, it is necessary to finally correct the position of the lens holding frame 30 at a predetermined position for preventing the shift of an image point at the zooming and the deterioration of an image quality.
To achieve the above, the cam follower pin 40 is consisted of an eccentric pin which is rotated to adjust the relative position of the zooming cam channel 11, rectilinear channel 21 and cam follower pin 40, whereupon the eccentric pin is fastened by an anchor screw.
However, the eccentric pin is displaced when fastened by the anchor screw, resulting in that the accurate positional correction cannot be obtained.
Japanese Laid-Open Utility Model Application No 61-179520 discloses a lens position correction device for a lens barrel in order to eliminate this problem.
More specifically, this device comprises an eccentric pin formed with a splined shaft and a lens holding frame formed with a splined hole which is engaged with the splined shaft, to thereby prevent the eccentric pin from displacing when fastened by an anchor screw after the positional correction.
Further, there has been proposed a technique wherein a polygon shaft and a hole engaged with the polygon shaft is provided instead of the combination of the splined shaft and the splined hole to prevent the eccentric pin from displacing when fastened by an anchor screw after the positional correction.
This correction of the position of the lens is necessary not only in the zooming but also in the focusing and the like.
These conventional lens position correction device for a lens barrel mentioned above has an advantage that the eccentric pin is not displaced when fastened after the correction of the position of the lens. However, this device has a disadvantage in that the driving amount during the correction of the position of the lens is only stepwisely obtained, so that a fine adjustment cannot be achieved.